extension_cli: Include the list of what an extension provides in the generated manifest (#24295)

This PR updates the Zed extension CLI with support for populating the
`provides` field in the generated extension manifest.

This field will contain the set of features that the extension provides.

For example:

```
"provides": ["themes", "icon-themes"]
```

Release Notes:

- N/A

crates/collab/src/db/queries/extensions.rs

@@ -1,3 +1,4 @@
+use std::collections::BTreeSet;
 use std::str::FromStr;
 
 use chrono::Utc;
@@ -370,6 +371,7 @@ fn metadata_from_extension_and_version(
             repository: version.repository,
             schema_version: Some(version.schema_version),
             wasm_api_version: version.wasm_api_version,
+            provides: BTreeSet::default(),
         },
 
         published_at: convert_time_to_chrono(version.published_at),